1. Field of the Invention
The present invention relates to a technique of an optical microscope, and more particularly, to a technique for preventing fungi from growing on an optical element provided in an optical microscope.
2. Description of the Related Art
Fungal growth on an optical element such as a lens, a prism, etc. is cited as one of factors to cloud an optics system of an optical microscope. Especially, fungal growth is a serious problem in the use of a microscope under a hot and humid environment.
Optical elements of an optical microscope are configured by combining many lenses, prisms, etc., and fungi can possibly grow on all of their surfaces. However, it is difficult in many cases to clean an optical surface depending on its type when fungi grow. Accordingly, it is vital to prevent fungi from growing (antifungal treatment) before they grow.
A technique for putting or coating an antifungal agent of a transpiration property on an inner wall of a microscope is conventionally known. With this technique, however, the antifungal agent fully transpirates, and loses its efficacy.
Additionally, Japanese Patent Application Publication No. H7-168001 discloses the technique for producing an antifungal efficacy by coating an optical element of a microscope with a photocatalyst. With this method, light having a wavelength on the order of 420 nm or shorter must be illuminated to activate a photocatalyst. However, general optical glass does not transmit ultraviolet rays. An optics system of a microscope, especially, an eyepiece lens of a microscope normally uses optical glass that does not transmit ultraviolet rays.
In the meantime, it is well known that illuminating ultraviolet rays significantly inhibits the growth of microorganisms such as fungi, etc. Japanese Patent Application Publication No. 2003-274930 discloses that even a light having a wavelength of 400 to 490 nm beyond ultraviolet rays also inhibits the growth of microorganisms, and encourages sporulation.